Discharge tube



Filed April 18, 1946 y 6, 1950 I F. COETERIER 2,508,228

DISCHARGE TUBE '3 Sheets-Sheet 1 INVENTOR ATTORNEY F. COETERIER May 16, 1950 DISCHARGE TUBE HF-T 2 Sheets-Sheet 2 Filed April 18, 1946 A TORNEY mama May is, 1950 FFICE DISCHAR'GE TUBE Frederik Coeterier, Eindhoven, Netherlands, al-

signor, by mesne assignments, to Hartford National Conn., as trustee Bank and Trust Company, Hartford,

Application April 18, 1946, Serial No. 662,971 In the Netherlands June 25, 1941 Section 1, Public Law 590, August a, 1946 Patent expires June 25, 1961 9 Claims.

This invention relates to a device in which is produced a beam 01' electrons and the velocity of the electrons in the beamis controlled by anontrol oscillation, whereupon the velocity variations are converted into intensity variations and an outputv voltage may be taken from the beam whose intensity is varied. Such a device is particularly suitable for producing, amplifying and/ or moduthe potential in the control space is higher than the potential at the boundary inquestion of the control space, whereas electrons entering the control space during the half cycle of the control oscillation, during which the potential in the con-- trol space is lower than the limiting potential. are accelerated, the average velocity of the electrons being so chosen, in conjunction with the length or the control space, that each electron traversing this space is influenced in the same way upon entering and leaving. the control space, so that the electron-beam comprises accelerated and retarded electrons after leaving the control space.

It has already been suggested to effect the conversion of velocity variations into intensity variations by means of a brake-field electrode which causes at least part 01' the electrons to reverse their direction of motion and is struck by the other electrons. By a proper choiceof the intensity of the brake-field it can be achieved that solely the electrons accelerated in the control space hit the brake-field electrode, whereas the. electrons retarded in the control space, whose velocity lies below a definite value, reverse their direction of motion in the braking field and are collected by one of electrodes bounding the control space. In this way separation of the retarded and accelerated electrons occurs, energy being withdrawn solely from the electrons accelerated in the control space, whereas the other electrons are 2 intensity variations is obtained, since in the electron beam leaving the braking field the electrons, which are accelerated in the control space and penetrate to a greater depth into the braking field; have been overtaken, by the retarded electrons. In this. case, however, a sharply defined conversion oi velocity variations into intensity variations is not obtaind, so that the efllclency of such a device cannot be high.

. According to the invention velocity variations are converted into intensity variations by means of a perforated brake-field electrode, by which the electrons whose velocity lies below a, definite value, are caused to reverse their direction during the conversion of velocity variations into intensity variations in such manner that these electrons traverse the control electrodesystem for the second time, whilst the direction of motion of the swi'fter electrons remains the same, the electrons traversing the control electrode system for the second time preferably supplying energy to a circuit connected to this system.

It is to be understood that it has already been suggested to make use of a not perforated brakefield electrode by which during conversion of velocity variations into intensity variations electrons, whose velocity is varied by a control-electrode system, are caused to reverse their direction in such manner that the electrons traverse the control electrode system for the second time and induce an oscillation in this electrode system.

The advantages of the device according to the invention, in which separation of the electrons accelerated and retarded in the control space takes place by means of a perforated brake-field electrode and solely the retarded electrons traverse the control-electrode system for the second time, will be more fully explained hereinafter by reference to the accompanying drawing in which:

Figs. 1 to 8 inclusive are schematic diagrams showing various electron discharge tube systems in accordance with the invention.

In the figures corresponding parts bear the same reference numerals.

Fig. 1 represents a device according to the invention which serves toproduce ultra-high frequency oscillations. This device comprises a discharge tube in which a beam of electrons is produced. The electrode system generating the beam of electrons comprises a preferably earthed cathode 2 indirectly heated by a filament, an accelerating electrode 3' having a constant positive voltage relatively to the cathode 2, and an electrode 4 whose purpose will be set out herein after and whose potential substantially corresponds to that of the cathode.

' cathode.

asoaaae Furthermore the tube i comprises a control electrode system consisting of a control electrode 5 and two bounding electrodes 8 and l by which the control space is sharply bounded, all of these electrodes having a higher positive direct voltage with respect to the cathode 2 than the accelerating electrode 3. The electrode 5 is connected to one end of a resonant. circuit 8, whose other end is connected to the bounding electrodes 8, I and, through the intermediary of a condenser 9, which constitutes a short circuit in regard to oscillations whose frequency corresponds to that of the resonant circuit 8, is connected to the cathode 2. The resonant circuit 8 is tuned-to the frequency of the oscillations to be generated. 1

At the side of the control space remote from the cathode 2 there is provided a perforated brake-field electrode III, which has supplied to it a small voltage which is negative with respect to the cathode. This voltage is chosen in such manner that the potential in the center of the aperture of the electrode it corresponds at the most to the potential of the cathode. This choice of the voltage loss between the brake-field electrode Ill and the adjacent electrode 1 of the control-electrode system, which voltage loss determines the intensity of the braking field, prevents the electrons, whose velocity is lower than the average value which is determined by the direct voltage supplied to the electrodes 5, t and 'I with respect to the cathode, from impinging on the electrode in and causes them to reverse their direction of movement in the pro ty of the brake-field electrode Ill. The electrons, whose velocity is higher than the average value, traverse the aperture of the brake-field electrode l and impinge on a collecting electrode ll having a positive voltage with respect to the cathode, which voltage preferably corresponds to the voltage of the electrodes 5, 8 and 'I relatively to the The collecting electrode II is connected to one end of an impedance, in the present embodiment a resonant circuit l2 tuned to the frequency of the oscillations to be produced, whose other end is connected to the cathode through a condenser It in regard to oscillations of the frequency of the resonant circuit II. A condenser It serves to earth the perforated brake-field electrode III for ultra-high frequencies.

The operation of the device represented in Fig. 1 may be explained as follows, it being assumed that oscillations, hereinafter called control oscillations, whose frequency corresponds at least substantially to the natural frequency of the circuit 8, are set up.in the circuit 8. In this case an electric alternating field prevails in the control space between the control electrode 5 on the one hand and the bounding electrodes 6 and I on the other hand, which acts upon the velocity of the electrons traversing the control space.

By a suitable choice of the average velocity at which the electrons enter the control space, and of the length of the control electrode 5 it can be achieved that the electrons traverse the control space in such a time as to be accelerated or retarded by both the said alternating fields in accordance with the moment at which the electrons reach the control space. In this case the beam of electrons leaving the control space exhibits a velocity modulation. with a shape of the control-electrode Ii as represented in the drawing an as strong as possible velocity modulation is obtained if the transit time of the electrons in the control space mounts to one or an odd number of half cycles of the control oscillation set up in the circuit I. a

The electrons whose velocity is varied and which issue from the control space find their way to the braking field which is produced by the electrode in and by which the electrons, which are retarded in the control space and whose velocity lies below the average velocity of the electrons, are caused to reverse their direction, whereas the'direction of motion of the electrons accelerated by'the two alternating fields in the control space remains the same. The last-mentioned electrons traverse the aperture in the electrode l0 and hit the electrode II which is connected to the resonant circuit l2. Consequently the brake-field electrode It causes separation of the electrons retarded and accelerated in the control space, the beam of electrons leaving the braking field being split up into two parts in both of which there occur succeeding maxima (groups of electrons) and minima of the electron density, in other terms the velocity variations of the beam of electrons have been converted into intensity variations by the braking field.

The intensity-modulated part of the beam of electrons, which leaves the braking field at the side facing the cathode, traverses the control space for the second time, but now in opposite direction and subsequently reaches the braking field prevailing between the bounding electrode 8 and the; electrode 4, which field has substantially the same intensity as the braking field of the a perforated braking-field electrode II. By a suitable choice of the distance between the perforated braking-field electrode i0 and the centre of the control-electrode system it can be achieved that the electrons of the groups of electrons cede energy upon traversing the control-electrode system for the second time. Due to this the velocity of the electrons retarded in the control space decrease still further, so that the groups of electrons leaving the control space at the bounding electrode 6 and vfinding their way into the braking field of the electrode-4 do not reach this electrode and reverse their direction of motion. After that the groups of electrons traverse the control electrode system for the third time and find their way again into the braking field set up by the perforated electrode l0, and so forth.

In this way the electrons retarded in the control space perform an oscillatory movement in the axial direction of the control-electrode 5, the groups of electrons traversing the controlelectrode for the second, or third time etc. ceding energy to the resonant circuit 8, which is connected to this electrode, and thus induce an oscillation in the circuit in question. The oscillation induced in the circuit now causes velocity control of the electrons in the beam of electrons as referred to above, as a result of which oscillations self-maintaining can be generated in the circuit 8.

In order to obtain the maximum efilciency of the electrons reversing their direction at the brake-field electrode I 0 it is desirable that the voltage applied between the perforated brakefield electrode and the neighbouring electrode 1 of the control-electrode system, in conjunction with the distance between the centre of the controlelectrode system and the brake field electrode It, should be chosen in such manner that the electrons cover the distance from the centre of the s,sos,aas

electrodeltotheelectrodellandbackinatime toorbeingamultipleoitheperiod corresponding of oscillation oi the resonant circuit I connected to the electrodes I. I mill. The same holds-for the distance between the centre oi" the; electrode I and thebrake-neld electrode 4. In this'case the'eiectrons emitted by the cathode and retarded in the control space, which electrons reverse their I direction at the .electrode it and subsequently at the electrode 4, andso on, willbe retarded by the alternfting fields prevailing in the said space whenever they traversethecontrol space, which involves a maximum delivery of energy by the electrons in question. l I

Since energy is withdrawn'from the electrons oscillating in the control space the velocity of the electrons steadily decreases, due to which the time in which the electrons cover the part oi the path extending in the control space, which path is covered by the electrons during one electron- 'that both the retarded electrons and the accelerated electrons cede energy whenever they traverse the control-space for the second, third time etc.

second, third time etc., the retarded electrons will cedeenergyii' they pass through the contract the control-space for the second time alter a time corresponding to the period of oscillation oi the con-' troI-oscillation or a multiple thereof: however,

with such a proportion oi the distance in quesoscillation, steadily increases; since, however. the

electrons penetrate every time to a smaller depth into the braking fields on either side of the contion the accelerated electrons will not cede enmay upon passim? for the second time. To such end it is necessary that the electrons reversing their direction should pass through the centre oi the control space tor the second time alter a time amounting to halt a period or to an odd number of half periods. 1

In case it is assumed that all velocityvarhv tions in the braking neld have been completely trol-electrode system. so that this part of the path Q ropulsion of the electrons in the beam the electrons after having made one or more oscillations, will,- lmpinge on an electrode of the control-electrode system. preferably on a bounding electrode. With a view to increasing the eillciency of the device it is desirable that the average number of oscillations, performed by the electrons, before they hit an electrode of the control-electrode system, preferably a bounding electrode I or I, should be as large as possible. To this end use may be made of a magnetic fleld'directed axially of the control-electrode I, whichileld may be produced by means of one or more coils or by means of one or more permanent magnets and by which the electrons are formed into a beam.

The intensity-modulated part of the beam of electrons which comprises the electrons accelerconverted into intensity variations. as a result oi the accelerated electrons being overtaken by the retarded electrons, and that consequently the groups of electrons traversing the electrode system for the second time are composed of retarded and accelerated electrons. these groups oi electrons, on passing for the second time, cede energy only if the electrons of these groups traverse the control-electrode system for the second time after a time amounting to 5/4. 9/4. etc. period the ated in the control-space, wanders through the aperture of the brake-field electrode i I to the collecting electrode II and sets up a voltage across the resonant circuit I2 in the output circuit of trons cover this distance in a time corresponding to half a period or an odd number of half periods oi the control-oscillation.

By means vof the circuit. arrangement according to the invention, in which the oscillations in the circuit I are maintained solely by the electronsretarded in the control-space, whilst the electrons accelerated in the control space deliver their energy to a circuit ll,-the advantage is obtained over the device referred to in the preamble that the obtainable eiliciency is much hi her.

Infect, in the device referred to in the preamble both the'movement of the electrons retarded in the control space and the movement of the electrons, accelerated in the control space are caused to reverse their direction by a brake-field electrode. In this case it is not feasible to choose the (I by the electrodes I and I. The control electrodes moment at which the electrons of the groups pass through the centre of the control space for the first time being determined'hy the moment at which electrons, which are positioned between the electrons that are retarded and the electrons that are accelerated on entering. pass through the centre.

Consequently in the device referred to in the preamble a compromise will have to be made in order to raise the efficiency as much as possible. In the device according to the invention, in which the retarded and accelerated electrons are separated, there is no question of a compromise and the device can be proportioned so that both the retarded and the accelerated electrons conver their kinetic energy into electric energy, thus obtaining a much higher efllclency.

. In the device represented in Fig. l the resonant circuit II, which may be used as an output circuit. is coupled solely by means of electrons to the resonant circuit I in which oscillations are generated. If desired the circuit I: may be 'coupled inductively or capacltatively or in some other way to the circuit I. In this case care is to be taken that the coupling should be made so that the oscillations set up in the two resonant circui support each other.

Fig. 2 represents a device according to the invention which substantially corresponds to the device shown in Fig. 1. In the deviceillustrated In Fig. 2 the electrode I has been omitted and the electrode I bounding the control space acts at the same time as an anode ior producing the beam of electrons. Furthermore the circuits I and II are united inone resonant circuit II, which is connected between the control electrode 8 and the electrode II, in which circuit oscillations are generated and from which oscillations can be taken in the manner set out above. Fig. 3 represents an embodiment in which, in contradistinction to Fig. 1, two control electrodes in and 5b are located in the control space bounded 5a and-5b are connected respectively to the ends of a resonant circuit l8. whose electric centre is connected to the limiting electrodes 6 and 'l and, in regard to oscillations with the frequency of the circuit ll, through the condenser 9 to the cathode 2. The control electrodes 5a and 5b and the limiting electrodes 6 and] have supplied to them a high positive voltage with respect to the cathode. The output circuit of the electrode includes a resonant circuit l2 from which energy can be taken.

The operation of the device shown in Fig. 3 is similar to that of the device shown in Fig. 1'. In this embodiment the average velocity at which the electrons enter the control-electrode system is-preferably so chosen, in conjunction with the length of the control-electrodes 5a and 5b in axial direction, that the electrons traverse each control-electrode in a time corresponding to a half period of the resonant circuit l2. Since two control electrodes are used the optimum emciency is obtained if the distance between the centre of the control electrode system and the perforated.

brake field electrode Ill, in conjunction with the voltage between the electrode l and the neighbouring electrode of the control-electrode system, is so chosen that the electrons pass through the centre of the control-electrode system for the second time after a time amounting to a half period or to an odd number of half periods of the oscillations in the circuit It. In this case the electrons returning at the electrodes Ill and 4 will in each instan'cecede energy upon traversing the control space for the second, third time etc.

If desired the circuit may be coupled again inductively or in some other way to the circuit It.

In the embodiment shown in Fig. 4 the circuit I6 connected to the control-electrodes is included at the same time in the output circuit of the electrode H in such manner that the oscillations set up in the circuit it are maintained not only by the electrons retarded in the control space, but at the same time by the electrons which are accelerated in the control space and reach the electrode l I. To this end the electrode II is connected to the end of the circuit l6 connected to the control electrode 5a, thus ensuring that an electron, which passes through the centre of the trodes 5a and 5b respectively and whose length control-electrode system and impinges on the electrode after a whole period of the oscillations in the circuit It or a whole multiple thereof, acts upon the circuit IS in the same way.

Fig. 5 represents a. simplified embodiment of the device shown in Fig. 4. The simplification conponds to'that of the device shown in Fig. 4, but

with the difference, that the acceleration and retardment of the electrons by means of the control oscillation supplied to the electrodes a and 521' takes place not upon entering a control space bounded by electrodes, but solely under the action of the alternating field set up between the electrodes 5a and 5b, whilstduring the time in which the electrons cover the path between the cathode and the control electrode in the velocity of the cuit It consists of a lecher-wire system in which the ends of the leads are connected to the elecamounts to one quarter or an odd number of quarters of wavelengths of the oscillations to be generated.

Furthermore the condenser I4 is interposed in the short-eircuitin bridge of a leeher-wire system 24, in which the ends of the leads are connected to the electrodes It and 4 respectively and of which the length, inclusive of the electrode supply leads in the tube amounts to half a wave-length of the oscillations to be generated. Such a device is eminently adapted for producing ultra-high frequencies. at which the electrode supply leads have a non-negligible inductance.

In the embodiment shown in Fig. 6, in which the control-electrode system comprises a controlelectrode 5 and two bounding electrodes I and the electrons accelerated in the control space,

after having traversed the perforated brake field electrode ID, are led along a second electrodesystem, the energy being taken of! through the intermediary of this electrode-system. The electrode-system in question consists of the electrodes l1, l8 and I9 and substantially corresponds to the electrode-system constituted by the electrodes 5, 6 and The electrode ll of the second electrode system is connected to one end of a resonant circuit 20 whose other end is connected to the limiting electrodes l8 and J8 and by passed to the cathode in regard to the oscillations whose frequency corresponds to that. of the circuit t.

To the electrodes l1, l8 and I9 is supplied a highpositive voltage with respect to the cathode 2. which voltage preferably corresponds to that supplied to the electrodes 5. 6 and I of the control electrode system. At the side of the second electrode system remote from the cathode there is provided a collecting electrode 2| which has a small positive voltage relatively to the cathode and serves to collect the electrons having trav-' ersed the second electrode system. In order to avoid secondary electron emission a perforated preferably grid-shaped electrode 22 is provided at the side of the collecting electrode 2| facing the cathode, which electrode 22 is connected to the cathode or has a small positive voltage relatively to the cathode, which voltage is lower than the voltage of the electrode 2| relatively to the cathode.

By a suitable choice of the distance from the perforated brake field electrode I. to the centre of the second control-electrode system, in conjunction with the velocity at which the intensitymodulated beam of electrons traverses the electrode-system in question, it can be achieved that upon traversing the electrode the groups of electrons induce in the resonant circuit 20 connected to this electrode an alternating voltage having the same frequency as that with which the traversing beam has been modulated in intensity or a harmonic thereof.

The greatest efiiciency is obtained if the length of the electrode IT, in conjunction with the velocity at which the electrons enter the second electrode system, is so chosen that the electrons traverse this electrode in a time correspondingto a half period or to an odd number of half period of the control-oscillation.

1s Similarly to the device shown in Fig. 1 the out put circuit II is connected solel by means of electrons to the self-oscillating part of the device.

The device shown in Fig. 6 affords the advantage over the embodiment shown in Fig. 1 that the electrons having traversed the second electrode-system can be braked before hitting the electrode 2|, as a result of which less'energy is lost'and the efliciencyof the device is enhanced. I

It is self-explanatoryjthat, if desired, the circuits I and 20 may be coupled together or united in one circuit which is interposed between the electrode 5 and the electrode l1 and whose electric centre is connected to the limiting electrodes 6, I, I8 and II. V

Fig. 7 represents an embodiment in which the control-electrode system corresponds to the device as shown in Figures 3 and 4 and in which energy is withdrawn by means of a second electrode system which comprises two output electrodes Ila and "b located in a space which is bounded by-the limiting electrodes l8 and I8. These electrodes are connected respectively to the ends of a resonant circuit 23, whose electric'centre is and to the cathode in regard to oscillations whose frequency corresponds to that of the resonant circuit. Since the electrodes I la, llb, l8 and ill have a high positive voltage with respect to the cathode, which voltage corresponds to the positive voltage of the electrodes 5, 5b, 6 and I relatively to the cathode, the limiting electrodes 6, I, II and I9 may be interconnected electric'ally inside or outside the tube and the condenser 9 serves for high-frequency earthing of the electric centre of both the circuit l6 and the circuit 23.

-In this embodiment a brake-field electrode is provided at the side of the second electrode system remote from the cathode, to which brakefield electrode is supplied a voltage which is negative relatively to the cathode and preferably corresponds to the voltage of the perforated brake-field electrode I 0 with respect to the cathode. This choice of the intensity of the braking field, which is determined by the voltage loss between the neighbouring electrode of the second electrode system and the brake-field electrode 25, prevents the groups of electrons, which have been retarded in the second electrode system, from hitting the electrode 25 and causes them to reverse their direction of motion in the vicinity of the said electrode, and to traverse the second electrode-system for the second time. By a proper choice of the distance of the electrode 25 from the centre of the second electrode system it can be achieved that the electrons cede energy also upon traversing for the second time. In this way the velocity of the electrons decreases still further so that the groups of electrons issuing from the second electrode system at the electrode it do not reach the electrode l0 and reverse their direction of motion again. After that the groups of electrons traverse the second electrode system for the third time and find their way again into the braking fi'eld produced by the electrode 25, and so on.

In this way the electrons accelerated in the control space perform an oscillatory movement in the axial direction of the electrodes Fla and Nb of the second electrode system. The correct the centre of the second electrode system' to the electrode 25 and back in a time amounting to half a period or an odd number of half periods of the oscillations produced in the circuit 23.

The embodiment shown in Fig. 7, in which the electrons retarded -in the" control space and the electrons accelerated in the control space are separated and are converted into groups of electrons which perform an oscillatory movement in the control-electrode system and the second electrode system respectively and during this movement cede in each instance energy to a circuit connected to the electrode system in question, permits a greater efficiency to be ob-' tained than the devices hitherto described, in which the electrons accelerated in the control space only once traverse the second electrodesystem.

It is self-explanatory that also in the embodiment illustrated in Fig. 6, in which the second electrode-system comprises one output electrode, a brake-field electrode may be provided at the side of the second electrode system remote from the cathode. by which brake-field electrode the direction of motion ofthe groups of electrons, which have traversed the second electrode-system, is reversed. In this case the largest delivery of energy is obtained, if the groups of electrons cover the distance from the centre of the second electrode system to the brake-field electrode and back again in a time which corresponds to the period or to a whole number of periods of the oscillations produced in the circuit connected to the output-electrode.

The embodiment shown in Fig. 8 is a simplified realisation of the device illustrated in Fig. 7, in which the limiting electrodes have been omitted and the control electrodes 5a and 5b, or the electrodes Fla and Nb, have a negligible di-' mension in the direction of motion of the electrons. The distance of these disc-shaped electrodes with respect to each other and with re. spect to the brake-field electrodes 4, 9 and 25 corresponds to the distance of the centre of the control electrodes or the output electrodes shown in Fig. 7, respectively, relatively to the said electrodes. 'The operation of the device, which entirely corresponds to that of the device shown in Fig. 7, will not be further described.

The device according to the invention, several embodiments of which have been described above, is particularly suitable for the production of ultra-frequency oscillations of cm.- or dm.-wavelength. In this case it is desirable that the resonant circuits shown in the figures should consist of lecher lines or concentric conductors, of which the electrode supply leads and the electrodes connected thereto may form part. Since it is desirable, moreover, that the conductors electrically interconnecting the various electrodes for the oscillations to be produced, should also be as short as possible, these connections are preferably established in the tube itself and, moreover, the arrangement of the electrode systems unmodulated oscillations have been described.

with reference to the figures of the accompanying drawings, but'the device according to the invention may also be used for amplifying, mixing or modulating oscillations.

aobaaae and to the second electrode system respectively.

The electrons retarded in the control space, which have their direction reversed by the perforated brake-field electrode I0, cause undamping of the resonant circuit connected to the control-electrode system, and in the device illustrated in Figures '7 and 8 undamping of the output circuit is obtained, since the electrons accelerated in the control space, after having traversed the output electrodes, reverse their direction and traverse the output electrodes for the second time.

The devices according to the invention, represented in the drawings, permit the obtainment of amplitude-modulated oscillations by supplying the modulated oscillations to an electrode, or electrode system, which controls the intensity of the cathode emission, as result of which the intensity of the electron beam entering the control space varies in the rhythm of the modulated oscillations. As an alternative modulated oscillation can be obtained by varying the voltage of the brake-field electrode, I0, 4 or 25 with respect to the cathode in the rhythm of the modulated oscillations.

Frequency-modulated oscillations can be ob tained by variation of the positive potential of the control-electrode system in accordance with a modulating oscillation. Thereby the average velocity, at which the electrons enter the controlelectrode system and consequently the period of an electron-oscillation in the control-electrode system and, consequently the frequency of oscillations produced in the resonant circuit connected to the control-electrode system, is varied.

What I claim is:

1. High frequency electron discharge apparatus of the velocity modulation type, comprising an envelope and within the envelope a cathode source to generate a beam of electrons, electrode means tovelocity modulate said beam, output electrode means for abstracting high frequency energy from the velocity modulated beam, and a. brake field electrode provided with an aperture and interposed between said velocity modulating electrode means and said output electrode means, said brake field electrode having a potential at which a portion of the electrons of said beam are returned to said velocity modulating electrode means and a portion of the said electrons are passed through said aperture to said output electrode means.

2. High frequency electron discharge apparatus of the velocity modulation type, comprising an envelope and within the envelope a cathode source to generate a beam of electrons and having a given potential, electrode means to velocity modulate said beam, output electrode means for abstracting high frequency energy from the velocity modulated beam, a first brake field electrode provided with an aperture and interposed between said velocity modulating electrode means and said 'output electrode means, said brake field electrode having a potential at which a portion of the electrons of said beam are returned to said velocity modulating electrode means and a portion of the said electrons are passed through said aperture to said output electrode means, and a second brake field electrode provided with an aperture and in.

terp'osed between said cathode and said velocity modulating electrode means and having a potential substantially equal to the potential of said cathode.

3. High frequency electron discharge apparatus of the velocity modulation type, comprising an envelope and within the envelope a cathode source to generate a beam of electrons having a having a potential at which the said electrons having a velocity less than the said average velocity are returned to said modulating electrode means and the said electrons having a velocity greater than the said average velocity are passed through said aperture to said output electrode means.

4. High frequency electron discharge apparatus of the velocity modulation type, comprising an envelope and within the envelope a cathode source to generate a beam of electrons having a given average velocity, electrode means to velocity modulate said beam and thereby accelerate a portion of the electrons of said beam to a velocity greater than said average velocity and decelerate a portion of said electrons to a velocity less than said average velocity, output electrode means for abstracting high frequency energy from the velocity modulated beam, a brake field electrode provided with an aperture and interposed between said velocity modulating electrode means and said output electrode means, said brake field electrode having a potential at which the said electrons having a velocity less than the said average velocity are returned to said modulating electrode means and the said electrons having a velocity greater than the said average velocity are passed through said aperture to said output electrode means, and means to electrically couple said output electrode means to said velocity modulating means.

' 5. High frequency electron discharge apparatus of the velocity modulation type, comprising an envelope and within the envelope a cathode source to generate a beam of electrons having a given average velocity, means to velocity modulate said beam and thereby accelerate a portion of the electrons of said beam to a velocity greater than said average velocity and decelerate a portion of said electrons to a velocity less than said average velocity, said velocity modulating means comprising two apertured boundary electrodes, an apertured control electrode interposed between said boundary electrodes and means to apply a modulating potential to said control electrode, output electrode means for abstracting high frequency energy from the velocity modulated beam, and a brake field electrode provided with an aperture and interposed between said velocity modulating means and said output electrode means, said brake field electrode having a potential at which the said electrons having a velocity less than the said average velocity are returned to said control electrode and the said electrons having a velocity greater than the said average velocity are passed asoaaas 1.5 through the aperture of said brake field electrode envelope and within the envelope a cathode source to generate a beam of electrons having a given average velocity, means to velocity modulate said beam and thereby accelerate a portion of the electrons of said beam to a velocity greater than said average velocity and decelerate a portion of said electrons to a velocity less than said average velocity, said velocity'inodulating means comprising two apertured bounding electrodes spaced apart, two apertured control electrodes arranged in alignment and interposed between said boundary electrodes and means to apply a modulating potential to said control electrodes in phase opposition, output electrode means for abstracting high frequency energy from the 'velocity modulated beam, and a brake field electrode provided with an aperture and interposed between said velocity modulating means and said output electrode means, said brake field electrode having a potential at which the said electrons having a velocity less than the said average velocity are returned to said control electrodes and the said electrons having a velocity greater than the said average velocity are passed through the aperture of said brake field electrode to said output electrode means.

7. High frequency electron discharge apparatus of the velocity modulation type, comprising an envelope and within the envelope a cathode source to'generate a beam of electrons having a given average velocity, means to velocity modulate said beam afid thereby accelerate a-portion of the electrons of said beam to a velocity greater than said average velocity and decelerate a portion of said electrons to a velocity less than said average velocity, said velocity modulating means comprising two annular electrodes spaced apart and having a central aperture and means to apply a modulating potential to said annular electrodes, output electrode means for bstracting high frequency energy from the ve ity modulated beam, a first brake field electrode provided with an aperture and interposed between said velocity modulating means and said output electrode means, said brake field electrode having a potential at which the said electrons having a velocity less than the said average velocity are returned to said annular electrodes and the said electrons having a velocity greater than the said average velocity are passed through the aperture of said brake field electrode to said output electrode means, and a second brake field electrode provided with an aperture and interposed between said cathode and said modulating means, said second brake field electrode having a potential substantially equal to the potential of said cathode.

8. High frequency electron discharge apparatus of the velocity modulation type, comprising an envelope and within the envelope a cathode source to generate a beam of electrons having a given average velocity, electrode means to velocity modulate said beam and thereby accelerate a' portion of the electrons of said beam to a velocity greater than said average velocity and decelerate a portion of said electrons to a velocity less than said average velocity, output electrode means for abstracting high frequency energy from the velocity modulated beam, a brake field electrode provided with an aperture and interposedbetween said velocity modulating electrode means and said output electrode means, said brake field electrode having a potential at which the said electrons having a velocity less than the .said average velocity are returned to said modulating electrode means and the said electrons having a velocity greater than the said average velocity are passed through said aperture to said output electrode means, an electron collector electrode arranged on the side of said output electrode means remote from said cathode source.

'and an electron permeable secondary emissive' electrode interposed between said output electrode means and said collector electrode.

9. High frequency electron discharge apparatus of the velocity modulation type, comprising an envelope and within the envelope a cathode source to generate a beam of electrons having a given average velocity, means to velocity modulate said beam and thereby accelerate a portionof the electrons of said beam to a velocity greater than said average velocity and decelerate a portion of said electrons to a velocity less than said 4 average velocity, said velocity modulating means comprising two apertured bounding electrodes spaced apart, a cylindrical control electrode interposed between said bounding electrodes and resonant circuit means connected to said control-- electrode, an output electrode arranged in thepath of the beam emerging from said velocity modulating means, load circuit means connected to said output electrode, a first brake field electrode provided with an aperture and interposed between said modulating means and said output electrode, said brake field electrode having a potential at which the said electrons having a velocity less than the said average velocity are returned to said control electrode and the said electrons having a velocity greater than the said average velocity are passed through the aperture oi said brake field electrode to said output electrode, and a second brake field electrode interposed between said cathode and said modulating means and having a potential substantially equal to the potential of said cathode.

FREDERIK COE'I'ERIER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,190,515 Hahn Feb. 13, 1949 2,312,919 Litton Mar. 2, 1949 2,393,284 Brown Jan. 22, 1948 2,414,843 Varian et al. Jan. 28, 1947 

